Transformer



Nov. 15, 1938.-

F. C. OWEN TRANSFORMER Filed Oct. 9, 1934 E'eder/GKC 014 672 ATTORNEYS 10 1 idleness; and to provide a construction in which Patented Nov. 1-5, 1938 UNITED STATES PATENT OFFICE 5 Claims.

The object ofthe invention is to provide a transformer in which the disadvantages due to its normally low power factor are overcome by equipping it with a reactance of a character to materially improve the power factor; to provide a construction in which the reactance is cut into and out of circuit, so that its beneficial effects may be had during load periods in the transformer without the disadvantage of the absorption of energy from the line during periods of the operation of cutting the reactance into and out of circuit is wholly automatic, but dependent entirely on the presence of a load in the secondary.

With this object in view, the invention consists in a construction and combination of parts of which a preferred embodiment is illustrated in the accompanying drawing, wherein the figure is a diagrammatic view of the invention.

The transformer illustrated is of the step-down t p being of the kind ordinarily employed in electric welding, and being of the magnetic les 1:- age type in which the primary I is wound in three sections on three different legs of the core I I. The secondary. llis wound on the remaining leg of the core, as well as on the diametrically opposite leg over the intermediate section of the primary.

The primary is energized from a suitable source and is controlled preferably by the double-pole single-throw switch it. The two terminals of the secondary are carried to the load, which, if the transformer be usedfor welding, for which it is particularly designed, will be dissipated in maintaining the are necessary to effect the weld ing operation.

The normally low power factor inherent in such a construction of transformer may be materially improved by the means of a condensive reactance, which, in the illustrated embodiment, consists of capacitors I, of which there may be a bank with the terminals connected to the terminals I! of a double-pole switch which normally assumes an open position but which is automatically moved to closed position. The switch terminals II, which are complemental to the terminals ii, are connected across the primary terminals of the transformer. When the switch is closed, therefore, the reactance is thrown directly across the primary, but when the switch is open, it is cut out of circuit. Thus there are provided beneiicial effects of the reactance without any of the disadvantages of its use, such as the absorption of charging current during periods of idleness of the transformer.

The operation of cutting the reactance into and out of circuit is made dependent on the transformer being under load, and to this end a supplemental coil I8 is disposedin surrounding relation to the core and its terminals are connected with an electrc-magnet I! which constitutes the actuating element for the switch. The magnet is is preferably an element of a stationary yoke 19 member 20, the extremities of which, when the magnet is energized, become magnetic poles exerting a magnetic pull on an armature 2| which carries the contacts ll.

When there is no load current in the second- 1 ary of the transformer, as when the welding operation is not being performed, if the transformer be designed for welding, there is practically no magnetic leakage from the core and hence no energy is present in the supplemental 20 coil l8. Immediately upon a load being imposed on the secondary, as when the welding operation is being carried on, the magnetic distortion taking place in the core results in a stray magnetic field which is effective to generate a current in 26 the coil l8, which becomes effective in the magnet 18, thereby causing the switch to be operated and the reactance to be thrown into circuit with the primary, thus effecting a material improvement in the otherwise poor power factor of the 80 apparatus. When thereis no load in the secondary, as when the welding operation is discontinued, there exists practically no stray field in the transformer core and accordingly thereis no current generated in the coil I! so that the magnet 86 i9 is then deprived of energy, preventing it from maintaining-the closed position of the switch,

which then drops to open position, thus cutting the reactance out of circuit, so that its employment does not represent a loss during idle periods as by the absorption of a charging current.

The invention having been described, what is claimed as new and useful is:

1. In combination with a transformer having a normally low power factor, a condensive reactance, an'electrically operated switch for connecting the reactance in one of the circuits of the transformer, and a coil for generating switch actuating current but related only inductively to an element of the transformer and generating actance across the primary, and a coil for energizing the switch, said coil having such an induction relation to the transformer as to limit it to generating the switch energizing current only when the secondary is under load.

3. In combination with a transformer having a normally low power factor, a condensive reactance, a magnetic switch for connecting the reactance across the transformer primary, and a supplemental coil for energizing the switch, said coil being disposed in surrounding relation to the transformer but responsive to core leakage in the latter only when the secondary is under load.

- 4. In combination with a transformer havinl a normally low power factor, a condensive reactance, a normally open magnetic switch for .former is under load, and a normally open magnetic switch for connecting the reactance across the primary of the transformer, said switch bein: energised from said coil.

FREDERICK C. OWEN. 

